Sen. Susan Collins Susan Margaret CollinsThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Billionaire who donated to Trump in 2016 donates to Biden Credit union group to spend million on Senate, House races MORE (R-Maine) is signing on to a bill to require campaigns to report foreign assistance offers to the FBI, giving the legislation its first GOP supporter.

"Russia’s efforts to interfere in our elections remain relentless. I’m proud to join Sen. @MarkWarner in cosponsoring the bipartisan FIRE Act to require presidential candidates to immediately call the FBI if they are contacted by a foreign power attempting to target our elections," Collins tweeted Tuesday.

Sen. Mark Warner Mark Robert WarnerFBI director casts doubt on concerns over mail-in voting fraud Democrats call for declassifying election threats after briefing by Trump officials It's time to upgrade benefits MORE (D-Va.), the bill's sponsor, announced earlier Tuesday that Collins had signed on, saying that Congress needed "to make it clear for presidential campaigns going forward: if a foreign power contacts you attempting to interfere in our elections, you call the FBI."

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But her support comes as election security legislation has emerged as an increasingly partisan fight in the Senate. Republicans have blocked attempts by Democrats to pass House bills, arguing that they are meant to politically benefit Democrats.

Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellTrump 'no longer angry' at Romney because of Supreme Court stance On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline The Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power MORE (R-Ky.) blasted his critics Tuesday accusing them of “lying” and “modern-day McCarthyism.” Minority Leader Charles Schumer Chuck SchumerPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' 3 reasons why Biden is misreading the politics of court packing Cruz blocks amended resolution honoring Ginsburg over language about her dying wish MORE (D-N.Y.) fired back that the GOP leader should bring a bill up for a vote if he didn’t like the criticism.

Under Warner's bill, campaign officials would have to report contacts with foreign nationals who are trying to make campaign donations or coordinate with the campaign to the Federal Election Commission, which would, in turn, notify the FBI.

The proposal shot into the spotlight after President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE suggested he would be open to accepting information on a political opponent from a foreign government.

“OK, let’s put yourself in a position: You’re a congressman, somebody comes up and says, ‘Hey I have information on your opponent.’ Do you call the FBI? You don’t,” Trump told ABC News last month.

Updated at 10:46 a.m.