Sen. Mark KirkMark Steven 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.

"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 CarperTrump states would bear brunt of gas tax increase: conservative groups Trump talk riles advocates on both sides of gas tax Senate bill would let EPA implement global greenhouse gas deal 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 PortmanCommittee chairman aims for House vote on opioid bills by Memorial Day Flake to try to force vote on DACA stopgap plan Congress punts fight over Dreamers to March 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 RockefellerJohn (Jay) Davison 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 WarnerLawmakers worry about rise of fake video technology Mueller indictment reveals sophisticated Russian manipulation effort GOP cautious, Dems strident in reaction to new indictments MORE (Va.), Bob CaseyRobert (Bob) Patrick CaseyDems hit stock buybacks in tax law fight Dem senator warns Mueller against issuing Russia report near 2018 election Dem praises gay US Olympian who feuded with Pence MORE Jr. (Pa.), Kay HaganKay Ruthven 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 McCaskillMcCaskill welcomes ninth grandson in a row Dem group launches M ad buy to boost vulnerable senators Senate Dems block crackdown on sanctuary cities 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) TesterWith vote against Brownback, Democrats abandon religious freedom Democrat Manchin: Pence attacks prove ‘they don't want bipartisanship’ in Trump admin Tester invited the Border Patrol Union’s president to the State of the Union. What does that say to Dreamers?   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 MurkowskiThe siren of Baton Rouge Interior plan to use drilling funds for new projects met with skepticism The 14 GOP senators who voted against Trump’s immigration framework MORE (R-Alaska) last week said her position on the issue was "evolving." Fellow Republican Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeFlake to try to force vote on DACA stopgap plan Congress punts fight over Dreamers to March Outgoing GOP rep: Republican Party 'heading into trouble' in election 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.