The Republican and Democratic presidential primaries are heading into the home stretch of some of the lengthiest battles in both parties' recent histories.
There are signals on both sides that the race could drag on until the final primary day of June 7, when California votes. And for Republicans, at least, the fight could go to the convention floor in July.
Five candidates officially remain in the race — though only two have mathematically realistic chances of claiming their parties' respective nominations before their conventions.
Two of the three remaining GOP candidates — Sen. Ted Cruz of Texas and Gov. John Kasich of Ohio — have mathematically impossible odds of obtaining enough delegates before the convention.
On the Democratic side, Sen. Bernie Sanders of Vermont needs a seemingly improbable turn of events, given Democratic primary rules that give more of an edge to the frontrunner at this point.
Nevertheless, they are all powering on, looking to stop frontrunners Donald Trump and Hillary Clinton.
With all that in mind, we take another look at who has the best chance of making it to the White House to succeed President Barack Obama.
Our rankings are based on the Real Clear Politics averages of national polls and those in states voting in coming contests (Pennsylvania, Maryland, Connecticut, and Indiana). We also factored in the candidates' delegate counts and their relative paths to the nomination, as well as their momentum (or lack thereof) over the past few weeks.
Here's a look at where all the candidates stand.
All poll results as of Monday.
SEE ALSO: Meet the average people who could determine whether Donald Trump wins the GOP nomination
5. John Kasich, Republican, Ohio governor
Kasich picked up momentum last month with a win in his home state's primary.
But the road before, and since, has been virtually empty for the Ohio governor. He has no chance to accumulate enough delegates to clinch the nomination before the convention, so he's banking that he can win a floor fight.
Kasich's rivals have seemed to grow increasingly frustrated with his presence in the race — Trump said he would "automatically win" if Kasich were to drop out of the race. Cruz, meanwhile, has shifted his stance on Kasich's presence in the race, teaming up with the Ohio governor in a last-ditch effort to stop Trump.
Those who talk up Kasich say he is a successful governor of a swing state with a record to point to and clear bipartisan appeal. He also has abundant experience from nearly two decades in Congress, including foreign-policy areas and his time as chair of the US House budget committee.
But that same bipartisan brand has hurt Kasich with the GOP base. He is to the left of most GOP candidates on immigration reform, and he expanded the federal Medicaid program under the Affordable Care Act — two issues that could doom him with hard-line conservatives.
National polling average among Republican voters: 22.3% (3rd)
Average in Pennsylvania, Maryland, Connecticut, and Indiana polls: 23.9% (3rd)
DELEGATES: 148
STOCK: Falling
Last month: 5
4. Bernie Sanders, Democrat, senator from Vermont
Sanders had perhaps the best single day of his campaign late last month, romping to landslide victories in Alaska, Hawaii, and Washington. But he got tripped up in New York, with a bigger-than-expected loss to Clinton in her adopted home state.
And he faces challenging odds — he needs to win about 71% of the remaining pledged delegates to overtake Clinton in the pledged-delegate count, according to NBC.
Moving forward, the map doesn't look especially favorable. In a system in which delegates are allocated proportionally, it will be hard for him to make up real ground in large states like California, Pennsylvania, New Jersey, and Maryland.
National polling average among Democratic voters: 46% (2nd)
Average in Pennsylvania, Maryland, Connecticut, and Indiana polls: 40% (2nd)
DELEGATES: 1,153
STOCK: Falling
Last month: 4
3. Ted Cruz, Republican, senator from Texas
Cruz always had favorable ground in Wisconsin. After that, the map was supposed to get more challenging — and it has.
Late April has overwhelmingly featured Northeast and mid-Atlantic contests more favorable to Trump — including delegate-rich New York, which Trump won with more than 60% of the vote. With more states from the regions on the map to come, Indiana's May 3 primary is looking more and more like a must-win for the Texas senator.
Still, Cruz inspires a flood of enthusiasm among the GOP base, and he may be the best-positioned candidate from within the political sphere to back up the notion that he's not a typical politician, that he is the outsider the base wants despite his day job in Washington.
National polling average among Republican voters: 30.3% (2nd)
Average in Pennsylvania, Maryland, Connecticut, and Indiana polls: 24.7% (2nd)
DELEGATES: 559
STOCK: Falling
Last month: 3
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