Sen. Mark KirkMark KirkHigh stakes as Trump heads to Hill Five things to watch for at Trump-Senate GOP meeting Giffords, Scalise highlight party differences on guns MORE (R-Ill.) announced his support for same-sex marriage on Tuesday, becoming the second sitting GOP senator to do so.

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"Same-sex couples should have the right to civil marriage," Kirk said in a statement on his blog.

"Our time on this earth is limited, I know that better than most," continued Kirk, who returned to the Senate earlier this year after a lengthy absence to recover from a stroke. "Life comes down to who you love and who loves you back — government has no place in the middle."

Kirk's statement came the same morning that Sen. Tom CarperThomas (Tom) Richard CarperAvalanche of Democratic senators say Franken should resign Overnight Cybersecurity: Mueller probe cost .7M in early months | Senate confirms Homeland Security nominee | Consumer agency limits data collection | Arrest in Andromeda botnet investigation Senate panel moves forward with bill to roll back Dodd-Frank MORE (D-Del.) also announced that he supports same-sex marriage.

The Human Rights Campaign, a pro-same-sex marriage group, praised the announcements by both Kirk and Carper.

"Sen. Kirk and Sen. Carper have shown tremendous leadership in announcing their support for marriage equality," Human Rights Campaign President Chad Griffin said. "It is a sign of our progress that so many of their colleagues are showing the same political will. Democrat or Republican, there can simply be no excuse for standing on the wrong side of history when it comes to this basic question of justice."

Kirk joins Sen. Rob PortmanRobert (Rob) Jones PortmanMcConnell names Senate GOP tax conferees Overnight Finance: House approves motion to go to tax conference — with drama | GOP leaders to consider Dec. 30 spending bill | Justices skeptical of ban on sports betting | Mulvaney won't fire official who sued him How four GOP senators guided a tax-bill victory behind the scenes MORE (R-Ohio), who switched positions in March, as the only sitting Republican senators to support gay marriage.

Last week, the Supreme Court held hearings on challenges to California's Proposition 8, which bans same-sex marriage and the federal Defense of Marriage Act (DOMA), which defines marriage as a union between a man and a woman. The legal challenges brought a flood of high-profile Democratic senators, including many from swing states or traditionally GOP strongholds, publicly supporting gay marriage.

Besides Carper, seven other Senate Democrats have endorsed same-sex marriage in recent weeks: Sens. Jay RockefellerJay RockefellerOvernight Tech: Trump nominates Dem to FCC | Facebook pulls suspected baseball gunman's pages | Uber board member resigns after sexist comment Trump nominates former FCC Dem for another term Obama to preserve torture report in presidential papers MORE (W.Va.), Mark WarnerMark Robert WarnerSenate panel moves forward with bill to roll back Dodd-Frank Comey back in the spotlight after Flynn makes a deal Warner: Every week another shoe drops in Russia investigation MORE (Va.), Bob CaseyRobert (Bob) Patrick CaseyThe Hill's 12:30 Report Avalanche of Democratic senators say Franken should resign Dems look to use Moore against GOP MORE Jr. (Pa.), Kay HaganKay HaganPolitics is purple in North Carolina Democrats can win North Carolina just like Jimmy Carter did in 1976 North Carolina will be a big battleground state in 2020 MORE (N.C.), Claire McCaskillClaire Conner McCaskillDemocrats turn on Al Franken Trump rips Dems a day ahead of key White House meeting The Hill's 12:30 Report MORE (Mo.), Mark BegichMark Peter BegichPerez creates advisory team for DNC transition The future of the Arctic 2016’s battle for the Senate: A shifting map MORE (Alaska), and Jon TesterJonathan (Jon) TesterGOP and Dems bitterly divided by immigration Senate panel moves forward with bill to roll back Dodd-Frank GOP defeats Schumer bid to delay tax vote MORE (Mont.).

Polls also show growing acceptance among the public of gay marriage, leading many in the GOP to adopt a softer stance.

Sen. Lisa MurkowskiLisa Ann MurkowskiMcConnell names Senate GOP tax conferees Week ahead: Trump expected to shrink two national monuments GOP on verge of opening Arctic refuge to drilling MORE (R-Alaska) last week said her position on the issue was "evolving." Fellow Republican Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeGOP strategist donates to Alabama Democrat Sasse: RNC help for Roy Moore 'doesn't make any sense' Sasse calls RNC decision to resume support for Moore 'bad' and 'sad' MORE (Ariz.) said that while he supported traditional marriage, he believed it "inevitable" that a 2016 GOP presidential contender could openly support gay marriage.

Updarted at 4:38 p.m.