In an abrupt about-face in strategy, Marco Rubio on Wednesday night attacked Donald Trump on policy by name from the stump, drawing the battle lines for a certain showdown with the GOP front-runner on the eve of Thursday's debate.

At an energetic rally in Houston, Rubio targeted Trump on Obamacare and Israel, charging Trump "thinks parts of Obamacare are pretty good" and that he's refused to come to Israel's defense.

"The front-runner in this race, Donald Trump, has said he's not going to take sides on Israel versus the Palestinians because he wants to be an honest broker," Rubio said. "Well, there is no such thing as an honest broker in that. Because the Palestinian Authority, which has strong links to terror, they teach little kids that it's a glorious thing to kill Jews."

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Rubio also alluded to Trump's claim that he can leave foreign policy details murky because he'll simply bring in the best advisers, telling the crowd, "We cannot have a commander-in-chief that is not ready the first day in office."

"You can’t just say, the way some people in this race have said — you’ll probably know what I’m talking about in a moment — you can’t just say, 'Well, when I get there I’ll hire the smartest people and they’re going to tell me what to do,'" Rubio said.

"The smartest people are already there. They’re already telling the president what he should be doing. He’s ignoring it. You deserve to know exactly what the next commander-in-chief is going to do," Rubio said.

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Rubio's efforts to dismantle parts of Obamacare and his experience on foreign policy in comparison to the rest of the field are key selling points in his pitch to voters, and it appears they'll become flashpoints in his clash with Trump.

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On Wednesday night, Rubio's communications team took the fight to Trump off-stage as well, with spokesman Joe Pounder suggesting Trump is complicit in the same "dirty tricks" he and Rubio have been attacking the Ted Cruz campaign for over the past few weeks.

Pounder called on Trump to repudiate a robocall reportedly telling voters in Vermont and Montana to not vote for "a Cuban, vote for Donald Trump."

"This is the lowest form of campaigning, and is the exact same type of dirty tricks Donald Trump has been decrying for weeks now," Pounder said.

The decision to take on Trump is a notable shift from just hours earlier, when Rubio was pressed on the "Today" show Wednesday morning about why he had, for weeks now, avoided a direct confrontation with the GOP front-runner.

"I didn’t run for office to tear up other Republicans," Rubio said, adding that he had only been attacking Cruz because "I’m responding to Ted Cruz," who has been clashing with Rubio for weeks on immigration reform and other policy issues.

"If I’m attacked, I’m going to respond and set the record straight," Rubio said.

But Trump didn't unleash the first attack — speaking after Rubio on the Today show, Trump said of Cruz: “So far, he’s been very nice and I’ve been very nice to him." But Trump warned "that could change."

And Rubio's decision to take aim at Trump Wednesday is all but certain to ensure that does change, and the two will likely clash on the debate stage Thursday.

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It's the final GOP debate before voters head to the polls for the Super Tuesday primaries. Although Trump holds a lead in most Super Tuesday states for which there's reliable public polling, Rubio's been executing a carefully calibrated strategy to gather delegates where he can carve out support in states that award them proportionally.

Up until now, that strategy saw Rubio largely training his fire on Cruz, with whom he's been competing to emerge as the alternative to Trump.

But on Wednesday, Rubio campaign manager Terry Sullivan said in a fundraising email that "the race looks even more like a two-man race now than it did this past weekend in South Carolina." Rubio finished second behind Trump in Tuesday's Nevada caucuses.

And Rubio's attacks on Wednesday night are further evidence that the campaign sees Cruz as a waning threat and Trump a necessary target — although whether Rubio can survive the clash remains to be seen. Every candidate that's attempted to take Trump down has so far fared the worse for it, seeing their support in the polls drop precipitously after Trump hits back.

Adding to the stakes for Thursday night's debate is the fact that last time Rubio came under heavy fire from an opponent on the debate stage — when Chris Christie hammered him as "robotic" during the debate before the New Hampshire primary — Rubio folded in a performance so disappointing it cost him at the polls.