The Fix's Aaron Blake explains why Donald Trump Jr.'s decision to tweet out emails about a meeting with a Russian lawyer could end up being damaging. (Peter Stevenson/The Washington Post)

It's a stunning admission by the president's eldest son: He met with a Russian lawyer promising dirt on Hillary Clinton after learning there was a concerted Russian effort to help his father win the election.

What Donald Trump Jr. admitted by publishing an email thread on Tuesday (right as the New York Times reported it) could carry some serious legal implications for him and the presidential campaign. But it also has political ones. Mainly, Republicans in Congress are struggling to come to the president's defense. Some tried and fell short. Others just didn't try at all.

Immediately after the news broke, their best defense was silence. 

Washington Post reporters tracking down lawmakers on Capitol Hill said Sen. Richard Burr (R-N.C.), chairman of the Senate Intelligence Committee that is leading Congress's Russia investigation, walked straight through a wall of reporters, stone-faced, and refused to answer questions.

In fact, even before Trump Jr. released the emails himself, Republican senators were practicing avoidance. Here's MSNBC reporter Kasie Hunt trying to track down Sen. Tom Cotton (R-Ark.):

Why this defense isn't a defense: It's the most visual example that Republicans can't defend what could be legally indefensible. If there was a clear explanation for Trump Jr. meeting with a Russian to get dirt on Clinton, they'd be giving it to reporters, not ducking them while the cameras and microphones are rolling.

Senate Majority Leader Mitch McConnell faced a barrage of questions on July 11, about the news of Donald Trump Jr.'s meeting with a Russian lawyer during the 2016 campaign. "They'll get to the bottom of whatever may have happened," he said. (The Washington Post)

Another attempt: Pivot to the media or the Obama administration. 

Sen. Ted Cruz (R-Tex.) did stop to talk to reporters, but as detailed here by Talking Points Memo, he refused to directly address the Trump Jr. news and the implications that the Trump campaign colluded with Russia.

“You’re being very persistent, and I suppose that’s your job,” Cruz told CNN's Manu Raju. “But let me point out the American people want the president to succeed.”

After being pressed by multiple reporters, Cruz finally said that the “irony” is that the Obama administration policies toward Russia “were constant weakness and appeasement.”

Why this defense isn't a defense: Trump uses this line all the time, especially since The Washington Post reported on President Obama's struggles about how and when to respond to Russian meddling in the 2016 election. “I feel like we sort of choked,” said one Obama administration official.

But Trump and Cruz are conflating two very different things. Obama was deciding how much to punish Russia for meddling; Trump Jr. appears to have admitted being open to working with the Russians to meddle.

And yet another attempt: To try to distinguish Trump Jr. from his father.

“Donald Jr. is very dedicated to his father, but you know he's not part of the administration,” Sen. Orrin G. Hatch (R-Utah), chairman of the Senate Finance Committee, told reporters.

Why this defense isn't a defense: It's true that Trump Jr. doesn't work for the administration. But he was a top adviser to the campaign, and as such, it's an open question of who knew what when, including the president. Trump's son didn't take the meeting alone. He invited Trump's then-campaign manager, Paul Manafort, and Trump's senior adviser and son-in-law, Jared Kushner, both of whom attended.

We'll keep this post updated as more Republican attempts (or lack of attempts) to defend the president come in.

Karoun Demirjian contributed to this report.