A theory of political ambition is developed in which political actors seek to increase their territorial jurisdiction and/or the size of their electoral constituency. Ease of entry and advancement into state and national politics, however, are shown to vary markedly across the nation. Strategic considerations play an important role in career decisions. Legislators take into account whether or not they will face an incumbent, the quality of likely opponents in primaries, the cost of campaigns, the relative value of their present office versus a higher office, and looming term limits. For example, as a result of term limits on state legislators, patient, highly selective, and successful moves up the political ladder have been replaced by early exits from office and riskier challenges for higher office. Those who are too liberal or conservative for their party and state are less likely to win statewide races. Distance from the "winning state party position" serve as a key to understanding which senators are reelected and which House members enter and win Senate primaries. It also explains why those preparing for statewide races shift their positions gradually over many years to improve their odds of success.