In a matter of months, George Walker Bush, 43rd President of the United States, could go down in history as the first full-term president in 175 years not to have exercised his Constitutional veto power.

That’s quite a feat considering his father, Bush Sr., vetoed 44 bills in his one term in office. His successor, Bill Clinton, vetoed 37 bills in his eight years—a little under par for recent presidents: Reagan vetoed 78, Carter 31, Ford 66, and Nixon vetoed 43 bills before being impeached.

In fact, only seven presidents in U.S. history have not used the veto. The last was James Garfield, sworn in March 4, 1881, who served less than a year in office before being assassinated by a disgruntled lawyer. In all, four of the seven veto-free presidents, Garfield, William Harrison, Zachary Taylor and Millard Fillmore, did not complete an entire term. And, the very last president to serve a full term without using a veto was John Quincy Adams, the sixth president.

So why is it that George Bush, one of the most politically controversial U.S. presidents, hasn’t used his veto power?

We know that Bush doesn’t have veto-phobia. As governor of Texas from 1995 through 1999, he vetoed 97 bills. From legislation providing lawyers for poor people to a Patient Protection Act, Bush freely wielded his red pen to block the Texas Legislature.

Instead, Bush’s no-veto record may in part be the result of an infrequent occurrence: the majorities in the House and Senate are of the same political party as the president. The Republicans in Congress are ideologically aligned with the president and have, for the most part, only sent him bills he would be inclined to sign. In addition, Karl Rove, Bush’s key political strategist, has advised against using presidential vetoes because they risk alienating interest groups friendly to the administration that benefit from Republican legislation.

Bush’s veto record may also be a reflection of an historical trend in American politics that resembles a rough bell curve: At the beginning of U.S. history vetoes were rare, in part because the federal government enacted less legislation. Presidents used them more as a check against unconstitutional legislation rather than as a political tool. From George Washington to Abraham Lincoln, the first 16 presidents averaged only 3.6 vetoes apiece. In that period Andrew Jackson held the record with only 12 vetoes.

For the next 100 years, from Andrew Johnson to Dwight D. Eisenhower, presidential vetoes exploded to an average of 118.9 per president. Franklin D. Roosevelt set the all-time record with 635 vetoes over his three and a half terms. Ideological battles in this era, from Reconstruction to the New Deal, fueled confrontation between the President and Congress. Moreover, as Rutgers University political scientist Ross Baker points out, this was also a time when “a large number of vetoes was seen as a sign of a vigorous presidency.”

It was only in the last four decades, starting with President Kennedy, that the average number of vetoes declined to 38.8 per presidency. Modern presidents, it seems, prefer to be seen as “uniters” rather than dividers. Of course, a veto threat can also be just as effective as the real thing, since Congress can only override a veto by a two-thirds vote from both houses. Since George Washington was sworn into office in 1789, presidents have vetoed 2,550 proposed laws and only 106 have been overridden.

According to the Office of Management and Budget figures, Bush has threatened to veto 40 bills, since taking office in 2001. So far the threat of a veto has been enough to achieve Bush’s political goals. In 2003 for example, two Senators, a Democrat and a Republican, co-sponsored the SAFE Act that would have revoked much of the PATRIOT Act. But a Bush veto threat intervened and consequently, despite broad bipartisan support, the SAFE Act was referred to the Senate Judiciary Committee and never came up for vote. But Bush’s veto-less record may be about to hit a speed bump.

For nine months Congress has been log-jammed on the highways and transit spending bill. The bill is currently in Conference Committee, where members are trying to hammer out the differences between the $318 billion Senate bill and the $283 billion House bill. But that isn’t the real problem. President Bush officially declared that he would veto any transportation bill over $256 billion. That spending limit is a priority for Bush to help bolster his “fiscally conservative” image that many see as flagging, given the gigantic 28.8 percent increase in federal spending since he took office (with non-defense discretionary growth of 35.7 percent)—the fastest rates of increase in 30 years.

With Congress expected to force a vote on the bill before the November elections, the president could be in a bind. While a veto might help demonstrate fiscal responsibility to his supporters, it could also highlight his inability to control the Congress’ profligacy at a crucial time in the presidential campaign.

Bush’s choice—to veto or not to veto-could impact not only his chances of re-election, but also whether he makes the history books as a member of a small exclusive club: the veto-free presidents.