The massive turnout is a reflection of organic enthusiasm among conservatives and a sophisticated effort by Trump’s campaign to rev up its get-out-the-vote machine ahead of the general election. Trump and Vice President Mike Pence traveled to Iowa and New Hampshire ahead of voting, and the campaign flooded the two states with high-profile surrogates and launched a Facebook advertising blitz reminding supporters to cast ballots.

The efforts are paying off, with Republicans turning out in historic numbers. Trump received more than 31,000 votes in the Iowa caucus, surpassing the 25,000 Democrats who turned out during Barack Obama’s successful 2012 reelection bid. Trump’s share was more than four times the number of Republicans who caucused during George W. Bush’s 2004 reelection campaign…

While it’s unclear what the figures might portend for the general election — the president’s job approval numbers remain stuck in the mid-40s in most surveys — the results highlight the degree to which Trump’s base is energized. A little more than a year after the president’s party suffered sweeping losses in the midterm elections, Republicans are bent on ensuring that Trump wins a second term.

“There is a personal vote for Donald Trump that is unshakeable,” said John Couvillon, a Louisiana-based pollster who has been tracking the primary totals. “Republican voters are willing to go out” to vote for Trump even though he doesn’t have a formidable primary challenge.