Democrat Jay Inslee maintained a 50,000-vote lead in the gubernatorial race Thursday night, and despite the long odds against a comeback, Republican Rob McKenna continued to insist he’ll close the gap and win as the final votes are tallied.

With an estimated 770,000 votes left to be counted, time is running out for McKenna, whose vote deficit has remained nearly unchanged since Election Day.

To catch up, the Republican would need to grab 54 percent of the remaining votes — a target he has not hit on any day of vote-counting so far.

In Thursday’s count, McKenna received 48.9 percent of the vote from the 20 counties that reported results. That’s an improvement from Election Day in those same counties, when he got 47.6 percent. But it was down from Wednesday’s tally when he got 50.4 percent.

If the vote in King County stays the same, McKenna would need 62 percent of the estimated remaining votes outside King County to pull even. McKenna is now getting 53.4 percent outside the county and 37.8 percent within.

Inslee, the former Democratic congressman from Bainbridge Island, already has started planning his transition team for the governor’s office.

But McKenna’s campaign was digging in for a fight — arguing that the outcome may not be known until the weekend or later. The two-term attorney general is trying to become the first Republican governor of the state in three decades.

Randy Pepple, McKenna’s campaign manager, recorded a video for supporters Thursday in which he scrawled out vote numbers on a whiteboard to explain his theory on why a win was still possible.

In a conference call with reporters Thursday night, Pepple said the campaign’s internal tracking polls showed late voters breaking for McKenna by 2-to-1. Two independent polls shortly before Election Day also showed a possibility that McKenna would do better among later voters.

Pepple declined to release the campaign’s polling: “You can either believe me or not believe me, I suppose.”

Sterling Clifford, an Inslee campaign spokesman, said the math continues to point to an Inslee victory. “The McKenna campaign seems to think they can lose a little on every sale and make it up on volume. The numbers just aren’t there for him.”