President Donald Trump stayed on message Monday night, resisting the temptation to weigh in on the day's congressional testimony about his wiretapping controversy.

In a cavernous Kentucky arena, with Senate Majority Leader Mitch McConnell just a stone's throw away, Trump instead called for a renewed dedication to dismantling and replacing Obamacare – the goal that has threatened to split an otherwise largely united Republican Party.

The health care bill winding its way through Congress, Trump said, 'is our chance to end Obamacare and the Obamacare catastrophe.'

The largest crowd to see Trump in person since his inauguration – estimated at north of 18,000 – cheered approvingly, even after booing McConnell loudly when he took the stage as a warm-up act.

McConnell, who has represented Kentucky in the U.S. Senate since 1985, pledged his support for 'our great new president who's going to give us the chance to fix this healthcare mess left behind by Barack Obama.'

U.S. President Donald Trump took the stage for a rally at the Kentucky Exposition Center in Louisville, Kentucky on Monday

More than 18,000 fans screamed and cheered despite a day of dispiriting news at the White House after FBI Director James Comey confirmed that there's an ongoing investigation into alleged ties between the president's campaign aides and Russians

Trump returned Monday to his political roots – the energy of a sternum-rattling arena crowd who love him – as he took his Obamacare replacement message on the road

Trump, too, seemed committed to the messy legislative process that will give right-wingers and moderates alike their chances to pick through House Speaker Paul Ryan's bill and dictate what the result looks like.

'We're going to negotiate, and it's going to go to the Senate, and back and forth,' the president said Monday.

'And the end result is going to be wonderful, and it's going to work great.'

McConnell accompanied Trump on Monday aboard Air Force One. Kentucky's junior senator, Rand Paul, was conspicuously missing.

Paul has said he will try to derail the American Health Care Act if it doesn't include a host of features that the president has promised will appear in 'phase two and three,' the next steps in a longer process dictated by congressional rules.

A House vote may come as soon as Thursday. Then come the Senate's fireworks.

Despite the dustup Paul has created, Trump paid him a compliment in front of his constituents – who applauded the mention of his name in a way McConnell didn't enjoy.

'I happen to like, a lot, Senator Rand Paul. I do. I like him. He's good. He's a good guy,' Trump said.

'And I look forward to working with him so we can get this bill pased in some form – so that we can pass massive tax reform, which we can't do until this happens.'

Trump clobbered Democrats and the 'fake news' media, and weighed in on a litany of issues including tax reform, law enforcement, veterans health care, Pentagon spending, North Korea, illegal immigration, terrorism, 'clean coal' and jobs

McConnell got more tepid applause even after Trump implored his rally crowd 'to give him a nice hand because he's on our side. You've got to take care of your people, right?'

'Are we going to be okay?' he asked McConnell, who sat offstage. 'Everything's looking good? Health care's looking good?'

Trump blasted Democrats in the House and Senate for what he called 'disastrous' impacts on the U.S. health care system stretching over the past seven years.

'They ignored the public, they ignored the voters, and they jammed a massiave health care takeover right through Congress,' he recalled.

'It's time for Democrat leaders in Washington to take responsibility for he disaster they and they alone created.'

The president also blamed the 'fake news' media – his favorite evergreen whipping-boy – for keeping public sympathies on Obamacare's side.

'If they told the truth about Obamacare, it would be so wonderful for the people of this country because it would sail right through – our plan would sail right through,' he said.

Monday's rally, organized by his presidential campaign organization and not by the White House, included mention a laundry list of Trump's pet issues.

Senate Majority Leader Mitch McConnell was booed loudly on Monday, until Trump implored his fans to give their own senator a round of applause

President Trump tweeted this aerial photo or unknown origin, showing what appeared to be some of the snaking line on a lawn past the furthest reaches of the Kentucky Exposition Center parking lot

Tax reform, respect for law enforcement, veterans health care and a defense buildup – 'We need it! A lot of bad actors out there, right?' – competed for space in his teleprompter-aided speech with North Korea, illegal immigration, terrorism, 'clean coal' and jobs.

'We are going to be a rich nation again,' Trump pledged.

Kentucky Sen. Rand Paul, a major fly in the ointment for the GOP's chances of replacing Obamacare, was nowhere to be seen at his home-state Republican rally, but Trump gave him a gracious shout-out

'You just worry about your basketball team. I'll take care of the rest.'

The University of Louisville men's team lost Sunday night to the University of Michigan in a championship tournament game they were favored to win, ending their season prematurely.

The president stayed on message more than he was accustomed to during the campaign, even in the face of loud protesters.

There were a total of seven on Monday night, including a trio who wore 'Black Lives Matter' t-shirts.

Trump, in mid-thought about Kentucky native Henry Clay – a former Speaker of the House and U.S. secretary of state – didn't skip a beat as police escorted them out.

The first interruption came from a woman who dangled a black 'anti-fascist' flag over an upper-deck balcony, and then tussled with two Trump fans who grabbed at it and ultimately won the tug-of-war.

She threw her middle fingers skyward, yelled 'F**k you! F**k you!" and turned away in disgust as police took her out.

Trump continued his sentence, praising the Electoral College, and didn't acknowledge her at all.

Throngs of Donald Trump supporters stood in line Monday – some for more than 12 hours – as the queue to see the president stretched more than a half-mile

Trump fashionistas in Kentucky sported 'Trumplican' cartoons and custom shirts designed to look like the 'wall' the president has vowed to build on America's southern border

While the president steered clear of commenting on FBI Director James Comey's blockbuster House testimony about wiretapping allegations he has leveled against former president Barack Obama, he did weigh in on the activities of the Senate Judiciary Committee nine hours earlier.

A man, who appears to be wearing a miner's uniform, waits for Trump to speak

Trump said Neil Gorsuch, his Supreme Court nominee, ' will uphold and defend the Constitution of the United States.'

'I urge members of both parties to swiftly approve his nomination. He is an outstanding man from an outstanding family with an unbelievably wonderful wife. They should approve.'

Half of Monday's story was about the crowd of screaming fans who came out in droves to see Trump.

A line snaked around the expo center, reaching more than a half-mile in length.

DailyMail.com walked the entire length of the queue – from front to back – and recorded video showing the throngs of supporters, the first of whom arrived 14 hours before showtime.

The footage was shot while Trump was still 600 miles away at the White House, more than three hours before he was set to speak, and hours after his administration suffered a body blow on Capitol Hill.

There was a queue stretching for around half a mile before Trump's appearance at the Louisville, Kentucky, arena

This family came in matching LEGO shirts – also promising a 'YUGE' wall (made of colored bricks!)

Reflecting on Trump's infamous slap at Hillary Clinton during a 2016 presidential debate, these besties wore shirts declaring: 'I am NOT a nasty woman'

The more than half-mile long snaked around the Kentucky Exposition Center, and started with a woman named Lynette who arrived at 5:30 a.m. for an event slated to begin at 7:30 p.m.

One man decided to show up to the rally as the man himself

FBI Director James Comey told the House Intelligence Committee that he knows of no evidence to support Trump's March 4 claims on Twitter that Barack Obama's administration wiretapped him at Trump Tower.

He also testified that there is an ongoing investigation into allegations of ties during the presidential election season between Trump campaign aides and individuals in Russian intelligence.

Trump backers, though, were in high spirits. None wanted to talk about the brewing controversies.

Instead they indulged in an unmistakably ebullient campaign atmosphere. Hundreds at a time shouted 'Trump! Trump! Trump!'

As the line grew longer and longer, others chanted 'Lock her up!' – a reference to former Democratic nominee Hillary Clinton.

One wore an outfit painted to look like a brick wall, a hat-tip toward his pledge to build a border wall between the U.S. and Mexico.

A family in line wore matching shirts showing a LEGO Trump building a brick wall – with the message: 'It's gonna be YUGE.'

Others dressed in gear identifying them as 'Trumplicans' and 'Proud Members of the Basket of Deplorables.'

Monday's rally, the second in as many weeks, takes place against a backdrop of a U.S. flag and twin sigs reading 'Promises Made' and 'Promises Kept.'

The Trump presidential campaign – not the White House – sponsored the event, which filled an expo center that has hosted the NCAA Final Four basketball tournament six times.

About 45 minutes before Trump was to appear, arena managers opened up upper-deck sections that had been roped off, accommodating a new crush of audience members.