SAN JUAN CAPISTRANO, California — In May 2016, fresh off a turn as one of President Barack Obama's chief congressional antagonists, Republican Rep. Darrell Issa threw his support behind Donald Trump's presidential bid and went on to campaign actively on Trump’s behalf.

A year later, Issa is on the defensive — under a drumbeat of criticism in his San Diego-area district for throwing his lot in with Trump, who lost California overwhelmingly to Hillary Clinton last year and whose recent actions healthcare, immigration and climate change have sparked widespread protest here.

Trump lost Issa's district to Clinton by a 7-point margin, helping push Issa into the scare of his political life: He barely held off an unknown Democratic challenger in 2016, winning re-election by just 1,600 votes in the closest House contest in the country.

Issa's now a top target for the Democratic Congressional Campaign Committee, which is eyeing several California Republicans as among the most vulnerable for re-election next year.

Issa is set to host a town hall meeting in his district Saturday, taking questions from constituents and braving all but certain outcry from progressive activists. Liberal groups and others eager to see Issa toppled have organized weekly demonstrations outside his district office since the election, and his most recent town meeting, in March, was rowdy and packed.

Issa found himself in a somewhat baffling situation earlier this week when he was photographed on the roof of his district office looking down at a throng of protestors who had gathered outside.

Mike Levin, a Democrat who plans to challenge Issa in 2018, tweeted a photo of Issa on the roof and accused the lawmaker of being "too afraid" to speak to his constituents. Issa tweeted his own account of what happened, saying he had chatted with constituents before heading up to the roof to take a picture.

Yes, this is really @DarrellIssa on the roof of his district office building. Too afraid to come speak with assembled constituents below. pic.twitter.com/wCYRjO8Ev8 — Mike Levin (@MikeLevinCA) May 30, 2017

It hasn’t always been this way for Issa, who made his name as chairman of the powerful House Oversight Committee from 2011-2015 when he was term limited out of the job.

With subpoena power and seemingly insatiable appetite for interrogating the Obama administration, Issa launched numerous probes into matters including the Benghazi diplomatic compound attack and whether the IRS at the White House's direction had allegedly targeted conservative groups.

Republicans cheered Issa's efforts, even as little in the way of genuine scandal was ever unearthed.

Spent the morning talking with constituents gathered outside the office today, then popped upstairs to take a quick pic! pic.twitter.com/K2CFdenOIj — Darrell Issa (@DarrellIssa) May 30, 2017

Now, absent that powerful perch, Issa has seen his influence diminish in Congress even as he faces persistent blowback for supporting Trump, including his vote in favor of the American Health Care Act which passed narrowly out of the House last month. Polls show the AHCA, which House Republicans rolled out as a replacement for Obamacare, is widely unpopular with voters.

Issa is also likely to be grilled at the town meeting on Trump's decision to withdraw from the Paris climate agreement. California, the most populous state by far, has for years taken a leading role in fighting climate change through legislation, regulation and business practices and polls here suggest voters have little interest in rolling back those efforts.

After Trump announced his plan to withdraw from the agreement on Thursday, California Democratic Gov. Jerry Brown announced the state would continue its aggressive plans to reduce carbon emissions.