There is a myth doing the rounds in liberal circles that the Republicans collude with oil companies to manipulate gas in the run up to the elections to favor the Republicans. This however is manifestly untrue.
See for example the gas prices for the two months before and after the 2004 elections:
Sep 06, 2004 181.5
Sep 13, 2004 181.3
Sep 20, 2004 183.9
Sep 27, 2004 189.5
Oct 04, 2004 190.2
Oct 11, 2004 194.9
Oct 18, 2004 198.4
Oct 25, 2004 198
Nov 01, 2004 198.6
Nov 08, 2004 195.1
Nov 15, 2004 191.8
Nov 22, 2004 190.1
Nov 29, 2004 190.3
Dec 06, 2004 186.8
Dec 13, 2004 179.9
Dec 20, 2004 177.7
Dec 27, 2004 175.4
(Weekly U.S. Regular Conventional Retail Gasoline Prices (Cents per Gallon))
Source: Department of Energy (numerous Excel sheets available. These number are from the "Regular" spreadsheet.
As you can see, in the week preceding the elections, gas prices were at a two month high, up almost 10% from early September. In fact they were at the highest level since June 7, and fairly close to the year-high of $2.02, but far removed from the year low of $1.49. Immediately after the elections, the gas prices dropped, to a low of $1.75 around New Year, and wouldn't hit the same level again until March 7, 2005.
Other election years don't show any meaningful impact of the gas prices, except 2006, where the gas price was 1 cent above the year-low at $2.19, down from a high of $3.00 in August, and 2002, when the gas price was almost at a year high during the election, up more than 30% from the year low.
Year Elect. high low
2006 2.19 3.00 2.18
2004 1.99 2.03 1.49
2002 1.43 1.44 1.08
2000 1.50 1.66 1.25
1998 1.00 1.09 0.91
1996 1.22 1.27 1.08
1994 1.12 1.17 0.99
1992 1.12 1.15 1.00