As voters prepare at last to choose their presidential nominees, Republicans face an uncomfortable question: Can any GOP candidate conceivably win an Electoral College majority this November?

The answer is “yes,” but it will be an uphill struggle.

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A Wall Street Journal analysis shows that genuine “swing states” have all but disappeared: 45 of the 50 states have voted for one party or the other at least four times during the last five elections. This pattern gives Democrats a big advantage: States worth 257 electoral votes have been reliably Democratic going back to 1996. The only swing states left are Florida, Ohio, Virginia, Colorado and Nevada.

To win this year, a Republican needs at least four of these five; a Democrat could win with just one. There’s scant room for error in putting together a plausible victory map for the GOP.