Donald Trump. Reuters/Carlo Allegri John Kasich and Ted Cruz announced late Sunday night that they would be joining forces in an attempt to stop Donald Trump.

Their goal is to prevent the Republican presidential frontrunner from reaching the needed 1,237 delegates to secure the GOP nomination before the party's July convention.

The plan has Kasich's campaign essentially conceding Indiana, the next state to vote, to Cruz. The Texas senator's campaign, meanwhile, will back out of Oregon and New Mexico and let Kasich, the Ohio governor, devote resources to the Western states.

But for Kasich and Cruz, the plan has three major flaws:

1. The math doesn't quite add up

Indiana, a state with 57 delegates on the line, is winner-take-all by congressional district and in the statewide vote. It's a huge state for the candidates looking to stop Trump — a win by him there would put him well on the path to the 1,237 delegates.

But it's not essential to Trump's endgame. Steve Kornacki of MSNBC recently projected that Trump could secure the nomination in the first ballot at the convention while winning just nine of the 57 delegates in the Hoosier State.

Nate Silver of FiveThirtyEight wrote that Trump would need 48 delegates in the state to eventually reach 1,237, but his equation did not factor in the number of unbound delegates from Pennsylvania who could vote for Trump on the initial ballot.

And in New Mexico and Oregon, two proportional primaries, both Kornacki and Silver projected that Trump wouldn't even need half of the delegates at stake to consider each a success.

2. Not all of Kasich's supporters will vote for Cruz — and vice versa

In Indiana, Trump holds a more than 6-point lead in the RealClearPolitics average of several recent polls. With Kasich polling at just under 20%, it's easy to assume that Cruz could overtake Trump if all of Kasich's supporters vote for the Texas senator.

But it's not that simple.

For example, in a recent Fox News poll, 22% of Kasich supporters said Trump was their second choice in the Hoosier State, while 53% said Cruz would get their vote if Kasich were out of the equation.

Sixteen percent of respondents had Kasich as their first choice.

With those numbers factored in, Trump's lead would shrink from 8 points to 3 points. But he would still be leading.

Also while the Kasich and Cruz campaigns have announced plans to "allow" the other candidate to "focus" on the states in question, neither has asked voters to vote for the opposite candidate in Indiana, New Mexico, and Oregon.

Indeed, when asked Monday for whom Indiana voters should cast their ballots, Kasich reportedly said, "They ought to vote for me."

3. It plays into Trump's 'rigged' argument

After Cruz and Kasich announced the plan to work together in an effort to block Trump, the Manhattan billionaire released a scathing statement on the pair that falls in line with his weekslong argument that the GOP's nominating process is "rigged."

"It is sad that two grown politicians have to collude against one person who has only been a politician for 10 months in order to try and stop that person from getting the Republican nomination," Trump said in the statement.

The appearance of two candidates joining forces specifically to block Trump from accumulating delegates seems to play into that argument.

"They are mathematically dead and this act only shows, as puppets of donors and special interests, how truly weak they and their campaigns are," Trump said in the statement, later adding, "Because of me, everyone now sees that the Republican primary system is totally rigged."

Trump has lambasted the delegate-selection process since Cruz began picking up delegates en masse in states such as Colorado and Wyoming, each of which held a convention instead of a more traditional primary or caucus. With the agreement between Cruz and Kasich aimed at minimizing the number of delegates Trump can acquire, the storyline is sure to flourish once again.

Trump said in the statement: "This horrible act of desperation, from two campaigns who have totally failed, makes me even more determined, for the good of the Republican Party and our country, to prevail!"