President Obama sent a thank you note to one of the Republican senators who agreed to meet with Judge Merrick Garland this week, the nominee to replace the late Supreme Court Justice Antonin Scalia.

"Thank you for your fair and responsible treatment of Merrick Garland," Obama wrote to Illinois Sen. Mark Kirk. "It upholds the institutional value of the Senate, and helps preserve the bipartisan ideals of an independent judiciary."

Kirk, who is the most vulnerable U.S. senator in the country this year, has been one of the most outspoken GOP opponents of Senate Majority Leader Mitch McConnell's decision to block the consideration of any Supreme Court nominee Obama puts forward this election year. That posture might help him appeal to the moderates and liberals he needs to survive a re-election campaign in the president's home state.

His suggestion that McConnell is being "close-minded" about the Supreme Court issue has earned Kirk the animosity of conservative legal activists.

"It is not 'closed-minded' to advocate for the rights of the people of Illinois to decide what kind of Court they want with their vote in November, instead of allowing the president to rush through another liberal only months before leaving the presidency," Carrie Severino, policy director at the Judicial Crisis Network, said last week. "Kirk's GOP colleagues are being democratic, and we suspect Kirk will learn a little something about that concept in November."

But the House Democrat challenging Kirk, Tammy Duckworth, says Kirk shouldn't expect Democrats to give him too much credit for his effort with Garland.

"Senator Kirk seems to expect extra credit for doing the bare minimum — in this case his job," Duckworth said. "While it's nice that he's meeting with Judge Garland, Kirk's cynicism was revealed when he told a conservative talk radio host that he didn't expect Mitch McConnell to allow the nomination to proceed."

Obama's stated gratitude undermines Duckworth's cynicism charge, making it no surprise that Kirk is touting the note. "Thanks @POTUS," Kirk replied in a tweet publishing the thank you note. "I met w/ Judge Garland because my responsibility to people of [Illinois] is more important than partisanship."