DES MOINES — With less than a month until the Iowa caucuses, Sen. Ted Cruz threw down the gauntlet Monday by embarking on a six-day, 28-event bus tour to solidify his status as the state's front-runner.

Cruz leads Donald Trump in recent polls of Iowans. He kicked off the tour amid new attacks from some of his Republican presidential rivals. This includes Trump, who said the Texas senator is copying his plan to combat illegal immigration.

"There have been more than a few insults and rocks thrown when it comes to the political race," Cruz told reporters before an event in Winterset Monday evening.

"I think it's interesting — a couple of weeks ago, almost almost every Republican candidate in the field was attacking Donald Trump. Today, almost every Republican candidate in the field is attacking me," Cruz continued. "It kind of suggests that something has changed."

The newly-minted Iowa favorite also touched on his strategy in the state, reiterating that he's committed to visiting all of Iowa's 99 counties. In the process, Cruz took a veiled swipe at Trump and Sen. Marco Rubio, saying that talking to voters face-to-face in the manner of the bus tour is more important than the occasional TV hit.

"At the very beginning, I committed to doing the 'full Grassley,'" he said, referring to the veteran Iowa senator who visits all 99 counties during his campaigns. "We're spending a lot of time in small, rural counties -- where men and women from Iowa can look you in the eye, can take the measure of the candidate. Are you telling the truth or are you blowing smoke? Who are you? That's the way campaigning should operate in Iowa. It doesn't work from a TV studio in New York City."

Joining Cruz on the trail all day was Iowa Republcian Rep. Steve King, who endorsed the Texan back in November. King, who didn't endorse a candidate in 2012, expressed optimism regarding Cruz's chances in 29 days. But even he acknowledged that the 2016 hopeful is now being seen in "a more negative way" because of the attacks.

"He's got to stay focused. He's got to stay on message — a positive message, but he's got to lay out this agenda for the future of America. That's there," King told Washington Examiner after an event in Boone, Iowa Monday morning. "The challenge is not getting sucked down in the abyss of negatives that's pouring forth here."

"It's like a game of political king of the hill. He's on top of the hill right now in Iowa at least. So they're trying to pull him off that hill, and they're fighting and trying to get a hold and drag Ted Cruz down," King said. "That's a component of politics, but we're seeing him in a more negative way than I've seen before. But the challenge is for him to stay positive, and for some of us to play a little defense [for him]."

Cruz's crowd sizes match his poll numbers. Events in Boone, Guthrie City and Winterset all attracted standing room only crowds, with caucus-goers both for him or not interested to hear the message he came to convey. Some, in fact, came from well out of state to up his chances in the Hawkeye State.

"I appreciate his honesty, his candor," said Claire Cosby, 63, who drove 900 miles from Tennessee to get out the vote for Cruz in Iowa. "He represents me. His values are in line with my values, and he's courageous. And when I say courageous, I mean that sincerely. If he tells you he's going to do something, he does it, and he's proven that he'll take a stand."

Day two of the "Cruzin' to Caucus" bus begins Tuesday with three stops, concluding with Sioux City in the evening.