Republican strategists have discovered a problem: Personal attacks on two of the most vulnerable Democratic senators are falling flat because of their likability.

Why it matters: In a broadly unfavorable national environment for Democrats, control of the Senate may rest on a pair of incumbents with two of the most compelling backstories in politics — Sens. Raphael Warnock of Georgia and Mark Kelly of Arizona.

• Warnock is the pastor of Dr. Martin Luther King Jr.'s Ebenezer Baptist Church.
• Kelly is a former astronaut and the husband of former Rep. Gabby Giffords, a gun control activist who survived an assassination attempt in 2011.

After failing to defeat Kelly and Warnock in crucial special elections that decided the fate of the Senate in 2020-21, the GOP is changing tack.

• The National Republican Senatorial Committee is now spending most of its money trying to tie Warnock and Kelly to President Biden and his dismal approval rating.
• "Whatever you think of them as people — you may like Mark Kelly, you may like Raphael Warnock — they have interesting stories, personal biographies," Chris Hartline, the NRSC's director of communications, told Axios. "But the reality is they both went to Washington and became part of the problem."

Flashback: Republicans in Georgia unsuccessfully sought to portray Warnock as a "radical liberal socialist" in the 2020-21 special election, while also targeting his personal history by dredging up old sermons and taking a 2002 arrest out of context.

• In Arizona, Republicans hit Kelly over his business record — in one NRSC ad, an animated astronaut dances as a narrator accuses Kelly of taking money from dangerous Chinese companies.
• That "attempt to sort of portray them as too liberal, extreme, shady cronies and whatever else, didn't cut through," Hartline acknowledged.

This year, the NRSC and other national Republican groups, including Senate leadership-aligned One Nation, are making a concerted effort to spend earlier in the cycle and hammer Democrats for supporting Biden at every opportunity.

• NRSC’s latest anti-Warnock ad acknowledges his "inspirational" story but targets his record as a senator voting with Biden 95% of the time.
• Ads against Kelly seek to undermine his nonpartisan persona and tie him to Biden on inflation and illegal immigration.

The other side: Democratic Senatorial Campaign Committee communications director David Bergstein said Kelly and Warnock's identities transcend the national climate. He pointed out that the two candidates outperformed Biden in 2020 and said Republicans will go into the general election with "deeply flawed" candidates.

• "Senate races tend to be candidate-versus-candidate contests. And both Sen. Kelly and Sen. Warnock have a strong identity, a strong record of service to their states, and they are backed by a unique and deep coalition that is drawn to them, not any one individual party," Bergstein told Axios.
• The GOP nominee in Arizona won't be decided until an Aug. 2 primary. In Georgia, Herschel Walker, Warnock’s GOP rival, has faced new scrutiny for reports of previously undisclosed children and inflated or false past statements, including claiming that he worked in law enforcement.

What they're saying: The Warnock campaign touted his efforts to cap insulin costs and lower prescription drug prices, fight proposed budget cuts to military bases in the state and address supply chain issues.

• A Kelly spokesperson said Arizonans elected him "because of his independence and Arizona-focused approach" and that he's focused on pocketbook issues and securing the border "even when that has meant standing up to his own party."

The intrigue: Jessica Taylor of the Cook Political Report said Warnock and Kelly must focus on their personal identities and brands to try to distinguish themselves from national Democrats.

• The key question: "Have they cultivated those personal brands enough where voters might trust them over Republican candidates?"