Originally Published: 13 SEP 22 07:01 ET

By Eric Bradner and David Wright, CNN

(CNN) -- New Hampshire Republicans are set to choose their candidate to take on Democratic Sen. Maggie Hassan on Tuesday in a primary that will lock in the final key matchup in November's battle for control of the Senate.

GOP voters in the Granite State are choosing among a field of candidates led by Don Bolduc, a retired Army brigadier general, and state Senate president Chuck Morse. Former President Donald Trump has not publicly backed a candidate in the race, but Bolduc has embraced Trump's election denialism. GOP Gov. Chris Sununu and national Republicans have rushed to defeat Bolduc, whom they view as a weaker general election candidate, and are backing Morse against Hassan.

In an evenly divided Senate, where Republicans need a net gain of just one seat to flip the chamber, Hassan is one of four key Democratic incumbents Republicans are looking to pick off this year. But as they have across the country, some candidates following in Trump's footsteps in New Hampshire have raised concerns among GOP leaders because of their lackluster fundraising and hardline right-wing rhetoric.

The primary in New Hampshire, which was thrown open after Sununu rebuffed national Republicans' efforts to recruit him, is a window into the GOP struggle that's been waged across the political map over the spring and summer.

Bolduc, who lost a bid for the GOP Senate nod two years ago, had brought in just shy of $600,000 by the end of August compared to Hassan's $31.4 million. He also has a penchant for saying controversial things, some of which he's walked back. But in response, Sununu called Bolduc a "conspiracy-theorist-type candidate" and "not a serious candidate" in an interview with WGIR last month.

In a Sunday op-ed in the New Hampshire Union Leader, Sununu wrote that "the stakes are too high for New Hampshire and America," adding that they need a nominee "who will have the resources to compete in the most crucial battleground state in America."

Still, Republican voters could once again ignore establishment preferences Tuesday and opt for the candidate who has aligned himself more closely with Trump, even if doing so comes at the cost of electability in November.

A pre-primary season of recruiting misses by top Republicans left the party without what it viewed as its strongest candidates in key races -- including governors like Sununu and Arizona's Doug Ducey, who opted against taking on Democratic Sen. Mark Kelly. Then, a summer of bruising Senate primaries -- many of them shaped by Trump's endorsements and pro-Trump voters' demands for candidates who embrace his lies about election fraud -- left Republicans fretting about the quality of the party's nominees and scrambling to close Democrats' fundraising advantage.

Republicans had hoped that inflation and the backlash new presidents historically have faced in midterm elections would carry the party to House and Senate majorities in November, delivering victories in competitive races across the map no matter the individual candidates in those races.

But gas prices have dropped. Biden and the Democratic-controlled Congress have enacted more of the President's agenda. Democratic candidates have outpaced most of their GOP Senate rivals in fundraising. The FBI's search of Trump's Mar-a-Lago estate has once again elevated a figure who galvanizes liberals and alienates suburban voters. And perhaps most significantly, the Supreme Court's June decision to end federal abortion rights protections appears to have animated parts of the electorate that Democrats feared would slip away from the party or sit the midterms out.

The early signs of a more evenly matched midterm landscape came in Democratic victories in a special election in a bellwether House district in upstate New York and in Alaska's ranked-choice special election for the state's at-large House seat, which has been in GOP hands for nearly half a century, as well as voters' overwhelming support for abortion rights in a referendum on the Kansas primary ballot.

Meanwhile, a handful of Republican candidates who won primaries, many with Trump's backing, have struggled to expand their appeal to a broader electorate in critical states -- including Arizona, Georgia, Ohio, Pennsylvania and Nevada -- that could decide which party controls a Senate that is currently divided 50-50.

GOP ups spending and focuses on crime

As GOP groups ramp up spending on television ads, their message in several key states is shifting away from attacking Biden on inflation. Instead, those ads target Democrats on crime and policing.

The latest example: In an ad launched Monday in Wisconsin, the National Republican Senatorial Committee labeled Lt. Gov. Mandela Barnes, the Democrat challenging Sen. Ron Johnson, "dangerous" and a "defund the police Democrat."

Barnes, in his own ad launched two weeks ago, said Republicans are trying to scare voters, and that their charge that he wants to defund the police is "a lie."

"I'll make sure our police have the resources and training they need to keep our communities safe, and that our communities have the resources to stop crime before it happens," Barnes says in the spot.

The shifting strategy underscores how unsettled the playing field is in the battle for control of the Senate just eight weeks from the November 8 midterm elections.

In August, Republican campaigns and groups spent $25 million airing over 160 ads about inflation, while also spending about $11 million airing 80 ads about crime, according to AdImpact data. In just two weeks of September so far, Republicans have spent about $9 million airing 89 ads about inflation, while also spending about $9 million airing 54 ads about crime.

In Ohio's key Senate race, Republican J.D. Vance launched an ad last week, saying, "Streets are exploding with drugs and violence, while liberals like [Democratic opponent] Tim Ryan attack and defund our police."

Ryan has repeatedly distanced himself from "defunding the police." In a recent ad in which he throws footballs at TV screens showing Republicans' ads, he says, "Here come the culture wars; I'm not that guy," as a football crashes into a screen showing the phrase "defund the police."

Democratic Senate candidates have so far vastly outspent their Republican rivals in races in Arizona, Georgia, Nevada, North Carolina, Ohio and Pennsylvania, forcing Senate Minority Leader Mitch McConnell-aligned outside GOP groups to attempt to make up the difference. As the campaign season shifts into a new gear post-Labor Day, Senate Leadership Fund, for example, is set to massively ramp up its spending. The super PAC has placed nearly $200 million in ad reservations over the next two months, according to AdImpact data, the most of any political advertiser.

It's picking up attacks in the crucial Pennsylvania Senate race, for instance, with an ad that highlights Democratic nominee John Fetterman's support for various prison reforms, echoing, "far-left John Fetterman, dangerously liberal on crime." Fetterman, like other Democratic nominees this year, has explicitly talked about funding the police.

FEC filings from SLF last week showed it upping its commitment in several key states -- adding $3.7 million to Pennsylvania, $3.7 million to Georgia, $3.5 million to North Carolina, $3 million to Ohio, $2.4 million to Wisconsin, and $2 million to Nevada. The additions will complement already massive reservations in battleground states. SLF had previously booked $38 million in Georgia, $33 million in Pennsylvania, $28 million in North Carolina, $27 million in Ohio, $19 million in New Hampshire, $16 million in Nevada, $15 million in Wisconsin, and $10 million in Arizona.

The GOP spending in North Carolina and Ohio underscores Democrats' success in expanding the map of competitive races. Both seats are held by retiring Republican senators, and are must-wins for the GOP's chances of winning the chamber in November.

In Florida, Democratic Rep. Val Demings has also outspent Republican Sen. Marco Rubio. Even though Rubio has long been favored to win reelection on the same ballot that features potential 2024 Republican presidential prospect Gov. Ron DeSantis, who is seeking a second term, Demings' nearly $25 million in TV ads has outpaced Rubio and Republicans by about a 4-to-1 margin. A big part of her message has been leaning into her experience as the former Orlando police chief to try to head off Republicans' attempts to tie her to her party's most liberal members. "I'll protect Florida from bad ideas like defunding the police," she said in one recent spot.

Debate about debates

Several key midterm match-ups are now in the midst of a debate about whether, when and how many times the candidates should debate -- including in Pennsylvania, where Fetterman, the Democratic lieutenant governor who suffered a stroke this spring, has committed to only one show-down with Republican Mehmet Oz, who has sought five debates.

Fetterman has said he would only debate in October. He said in a statement that he always intended to debate Oz and that the hold-up has "only ever been about addressing some of the lingering issues of the stroke, the auditory processing, and we're going to be able to work that out," but he didn't provide specifics.

"Let's be clear - Dr. Oz's campaign won't agree to a SECRET debate. It has to be a REAL one with REAL journalists asking REAL questions. Sorry John - imaginary debates don't count!," Oz communications director Brittany Yanick said in response.

While Oz's team has been raising questions about Fetterman's health, the Democrat has hammered Oz over past remarks calling abortion "murder," with his allies warning Sunday that Oz would be a "rubber stamp" for a national ban.

"Women are the reason we can win," Fetterman said at a rally in the Philadelphia suburbs. "Don't piss women off."

In Georgia, Democratic Sen. Raphael Warnock and his Republican challenger, former University of Georgia football star Herschel Walker, have engaged in a months-long debate about debates.

Walker refused to participate in a debate during the GOP primary. Warnock has sought three debates, and Walker has said he'd debate Warnock on October 14 in Savannah. Warnock responded by saying he would debate Walker then, if Walker would accept another debate.

A person familiar with the Republican candidate's thinking told CNN last week that Walker is not going to agree to another debate, effectively sending both candidates back to square one.

Debates typically drive news coverage of key races in their final weeks. The limited number in several key races, including Pennsylvania and Georgia, could increase the importance of television ads as the primary way of reaching voters -- a reality that explains why McConnell and other top Republicans have increased outreach to major donors and urged senators to transfer campaign cash to the Senate Leadership Fund.

"The Democrats are going to vastly outspend Republicans across the board. But as long as we have enough money to tell our story and to defend our opposition, I think we'll be fine," Texas Sen. John Cornyn, a member of McConnell's leadership team, said last week.