GOP frontrunner Donald Trump faces a key test as five large states, with rich troves of delegates, vote on Mega-Tuesday.

While Trump has the lead in delegates, he hasn’t yet won a majority of the votes in any primary or caucus. He needs to expand his support to push the party to consolidate behind his candidacy.

According to RealClearPolitics, Trump has 460 delegates, 90 more than second-place Texas Sen. Ted Cruz with 370. Florida Sen. Marco Rubio is a distant 3rd with 163, followed by Ohio Gov. John Kasich with 63.

While Trump has the most delegates, his total only represents about 43 percent of the delegates awarded to date. This is a bit higher than his share of the Republican vote so far. Trump has won most states with support levels in the mid to high 30s. Only a few times has Trump crossed the 40 percent threshold in support.

Trump hasn’t yet won a primary or caucus with a majority of the vote. By comparison, Mitt Romney, the 2012 nominee, won his first contests with an outright majority on Super Tuesday, March 6th, that year.

Trump obviously benefited in the early stages of the campaign by a very large Republican field of candidates. In the last few weeks, that field has narrowed considerably and is likely to winnow even further after votes on Mega-Tuesday.

If Marco Rubio loses Florida, as expected, it is likely he will abandon his campaign for the nomination. So too John Kasich, if he fails to beat Trump in Ohio. Polling on the eve of the Ohio vote, however, gives Kasich an edge in his home state.

There are 368 delegates at stake on Mega-Tuesday. Florida and Ohio are the biggest single prized, awarding 99 and 66 delegates respectively, to the winner of the statewide vote. Another 193 delegates are awarded in Missouri, Illinois, and North Carolina on a somewhat proportional basis. The Northern Marianas Islands award nine delegates to the winner of that territory’s caucus.

If Trump wins Florida, Ohio, and earns around 40 percent of the delegates awarded proportionally, he will still have less than half the delegates awarded to date. Keep in mind, that would be an enormous sweep of the Mega-Tuesday contests for Trump.

While that result would give Trump a much larger lead in delegates over Cruz, his second place rival, it still wouldn’t give him a majority of the delegates that have been awarded.

Such a result would also prompt Kasich and Rubio to leave the nomination contest, creating a head-to-head match-up between Cruz and Trump. Trump would still need to win around half of the remaining delegates to clinch the 1,237 necessary to secure the nomination.

In other words, Trump would have to defeat Cruz is almost all of the states still to vote, the majority of which award delegates proportionally. If Kasich wins Ohio, however, the difficulty of Trump reaching the delegates needed becomes even more complicated.

While Trump could very well enter the Republican convention with the most delegates, he may be short of the minimum number needed to secure the nomination outright. In that situation, the majority of delegates will be pledged to someone other than Trump.

One can easily imagine a scenario where the three candidates with the bulk of delegates negotiate a deal among themselves to nominate someone other than Trump.

Trump can avoid this scenario by expanding his support. Despite his dominance in the polls, he is still leading simply because the opposition remains divided. In his best states, he is still winning the support of around 40-45 percent of Republicans. It can still be argued, then, that a majority of Republicans don’t support Trump.

Winning some states with a majority of the vote would go a long way to achieve the consolidation in support that Trump now seeks. While many in the media and in the Trump orbit would like to argue that the nomination race is nearing its end, that is far from the case.

It won’t begin to be the end until Trump can begin to win some primaries with a majority. No Republican nominee in recent memory has gone so deep into the nominating contests without securing such a victory. Trump needs to grow his support soon.