The Broncos, however, might not be No. 4 for long.
Oregon, despite a two-point victory at California, remained No. 1 with a BCS average of .9753. Auburn remained No. 2 at .9687, and TCU remained third at .8966.
Boise State is fourth at .863 but cut TCU's points lead in half.
The Horned Frogs overtook Boise State last week with an emphatic victory at undefeated Utah but lost ground this week with a closer-than-expected win over San Diego State, coupled with Utah's blowout loss at Notre Dame.
Boise State is coming off one of its best games of the season, a 52-14 rout at Idaho in which the Broncos led 45-0 less than a minute into the second half.
ESPN's BCS expert, Brad Edwards, had predicted last week that TCU would stay ahead of Boise State if both teams won out.
But Edwards said on ESPN's BCS show Sunday that "the ball is in Boise State's court."
This was huge news considering the order of the standings did not change.
LSU is fifth again, followed by Stanford, Wisconsin, Nebraska, Ohio State and Oklahoma State.
Boise State jumped back over TCU in both BCS polls — USA Today and Harris — and into the No. 3 position behind Oregon and Auburn.
TCU's computer average dropped one spot to No. 3, and Boise State's dropped one position to sixth. But Boise State can expect to close that gap if it wins its final three games.
The Broncos host Fresno State on Friday, then travel the following Friday to BCS No. 18 Nevada, which escaped Fresno on Saturday with a 35-34 victory.
Boise State closes the season at home on Dec. 4 against Utah State.
TCU has only one game left, at lowly New Mexico. The Horned Frogs seemingly have little left to show the voters or input into the BCS computer component.
The top two teams in the final BCS standings on Dec.5 will play for the national title on Jan. 10 in Glendale, Ariz.
There is, however, more than the title game at stake.
If Oregon and Auburn end up playing for the championship, the Rose Bowl must take the highest-ranking school from a non-automatic-qualifier conference, which figures to be either Boise State or TCU.