If you’re running for your party's presidential nomination, you'd better not rely on the notion that you have the best chance of being elected in the general election. The most compelling evidence at the moment is John Kasich's campaign—that is, its lack of success.

Kasich and his campaign manager John Weaver emphasize the electability issue day after day. They point to polls that show Kasich running ahead of Hillary Clinton in one-on-one matchups. "Nearly every poll shows that both Trump and Cruz will get crushed by Hillary Clinton in the fall," Weaver said in an email. "If we want to win the White House, there is only one Republican candidate who can defeat Hillary." Kasich.

The problem is a simple one: Voters in primaries are rarely persuaded by this argument. Even if they believe electability matters, they tend to believe the candidate they favor is electable. This is especially true when Republicans look at Clinton as the Democratic nominee. They think she's beatable by their candidate, even if polls indicate otherwise.

Charlie Black, who's been involved in GOP presidential races since 1972, says electability has never worked in primaries. "I've tested it over the years in polls," Black says. "Primary voters don't care about electability."

Exit polls bear this out. In last week's Wisconsin primary, only 11 percent said electability was "the top candidate quality." In contrast, 34 percent said the top quality was that a candidate "shares my values," 34 percent said a candidate's ability to "bring change" mattered most, and for 20 percent the most significant quality was telling it "like it is." Kasich finished a distant third in Wisconsin with 14 percent of the vote.

Voters in other primary states were similarly indifferent to electability. In New Hampshire, 12.4 percent said it was what they looked for in a candidate. Kasich came in second with 15.8 percent, his best showing except for Ohio, his home state. In Ohio, which Kasich won with 46.8 percent, a mere 10 percent rated electability first.

Tales of electability as a campaign issue invariably have the same ending: It didn't work. In 1976, when Ronald Reagan challenged President Gerald Ford for the nomination, the Ford camp declared him unelectable. Reagan lost the nomination narrowly, but got one million more votes than Ford in the primaries.

In 1980, Reagan was again said to be unelectable by his GOP opponents. Nonetheless, he swept most of the primaries. He defeated President Jimmy Carter by 10 percentage points in the general election, though Carter's aides initially regarded Reagan as a certain loser.

In 2012, the calling card of Utah governor Jon Huntsman was his supposed electability. It was tested in New Hampshire. He finished third with 16.9 percent and soon dropped out of the race.

Later in 2012, Newt Gingrich and his fellow Republican candidates were pressured to lay off tough criticism of Mitt Romney because he was electable against President Obama and they weren't. They refused to muffle their criticism. Though their attacks may have hurt Romney slightly, they weren't a major reason for his loss to Obama.

This year, Marco Rubio invoked electability in the waning weeks of his campaign. Indeed, polls showed he would be the strongest Republican candidate against Clinton. "That's just not the way most voters vote," at least in the primary phase of a presidential contest, Rubio's pollster Whit Ayres says. Rubio dropped out on March 15 after losing in his home state of Florida to Donald Trump.

The most telling evidence is how well the two least-electable candidates in polls against Clinton—Trump and Ted Cruz—have fared in the race for the nomination. Trump is first in delegates, Cruz second. Trump has won 21 contests, Cruz 14. Kasich has won only Ohio.

Yet the Kasich forces insist everything will change if the Republican convention is contested. Kasich has said the convention may be "magically" affected in his favor. His lead over Clinton in polls will be taken seriously. Weaver cites an average of eight polls that show Trump behind Clinton by 10.8 percentage points and Cruz trailing by 3.1 points. Kasich leads Clinton by 6.3 points.

Trump and Cruz "are terrified to face Gov. John Kasich at a convention because they know that delegates will select the candidate who is not only the most prepared to be President, but can also defeat Hillary Clinton: John Kasich," wrote campaign chief Weaver in one of his many emails.

But Kasich faces two obstacles. The first is getting on the convention ballot. For that to happen, the rule must be tossed out that requires a candidate to win the most votes in eight states to be on the ballot. Trump and Cruz have met the eight-state rule, but Kasich cannot. He'll need the delegates—a large majority of whom are in the Trump or Cruz camps—to vote to rescind the rule. Then Kasich would have to beat Trump and Cruz to win the nomination.

Black, the wisest and most experienced of Kasich's advisers, thinks this scenario is possible. The delegates will be dominated by party regulars and activists who will see Kasich as "a successful two-term governor" in a critical state, he says. It's the longest of long shots. A heavy dose of magic will be required.

Fred Barnes is an executive editor at The Weekly Standard.