FYI - the commonly-referred to "93% of the time" figure refers either to the fact that Kerry voted the same as Ted Kennedy 93% of the 28% of the votes he attended in 2003, or to a "93" score assigned senators by a liberal group (see below).
From the Washington Post: http://www.washingtonpost.com/ac2/wp-dyn/A22260-2004Feb7?language=printer
Kerry's 19-year record in the Senate includes thousands of votes, floor statements and debates, committee hearings and news conferences. That long paper trail shows that, on most issues, Kerry built a solidly liberal record, including support for abortion rights, gun control and environmental protection, and opposition to costly weapons programs, tax cuts for wealthy Americans and a 1996 federal law designed to discourage same-sex marriages.
But there are exceptions to that generally liberal voting record. Kerry voted for the welfare overhaul bill in 1996 that President Bill Clinton signed over the vociferous opposition of the party's liberal wing; supported free-trade pacts, such as the North American Free Trade Agreement that organized labor opposed; backed deficit-reduction efforts in the mid-1980s, which many other Democrats opposed; and was distinctly cool toward Clinton's health care proposal, which died after being pilloried as the embodiment of big government.
From http://www.nationalreview.com/york/york200401220835.asp
For example, Kerry has earned a lifetime rating of 93 from the liberal Americans for Democratic Action, which selects key votes each year and rates lawmakers according to a perfect liberal score of 100.
Viewed from the other side of the ideological divide, Kerry has a lifetime rating of six from the conservative American Conservative Union, which uses a similar methodology to rate lawmakers according to a perfect conservative score of 100. Kerry's rating is the same as Leahy's and New York's Charles Schumer's, although it is slightly less liberal than Kennedy's lifetime rating of three.