The final fifteen months of Carter's presidential tenure were marked by several major crises, including the Iran hostage crisis, serious fuel shortages, and the Soviet invasion of Afghanistan. Ted Kennedy, a prominent liberal Democrat who protested Carter's opposition to a national health insurance system, challenged Carter in the 1980 Democratic primaries. Boosted by public support for his policies in late 1979 and early 1980, Carter rallied to defeat Kennedy and win re-nomination. In the general election, Carter faced Reagan, a conservative former governor of California. Though polls taken on the eve of the election showed a close race, Reagan won a decisive victory. In polls of historians and political scientists, Carter is usually ranked as a below-average president.