Our updated blog on the more than 600,000 votes cast for withdrawn candidates includes a spreadsheet where we show the total votes earned by all the Republican and Democratic candidates for president. We rely primarily on Politico's results page, which will differ in some states from the final certified vote totals. Furthermore, given that many states held lower turnout caucuses and how some of those states (such as the Democratic caucuses in Iowa) don't report popular vote totals, it's not a truly fair way to measure relative strength of candidates. At the same time, the results ares instructive about where things stand.
Comparing Democrats: In the contests to date, Hillary Clinton has earned a total of at least 8,942,728 votes (57.2% of all cast in Democratic contest), Bernie Sanders has received 6,417,291 votes (41.0%), and others have a total of 1.75%.
Comparing Republicans: Donald Trump has at least 7,825,555 votes (37.1%), Ted Cruz 27.3%, withdrawn candidate Marco Rubio has 16.3%, John Kasich has 13.3% and the rest of the field 5.9%
Comparing Democrats to Republicans: Clinton has more votes than any Republican, but Republicans overall have had at least 21,069,602 votes cast in their contests compared to 15,637,903 in the Democratic contests. One statistic to keep an eye on is whether Bernie Sanders can surpass Trump and other Republicans in the national vote -- which is only possible if Democratic turnout rises, Sanders starts winning large population state primaries, and the Republican field remains split. (As reported earlier, both Sanders and Clinton in Michigan and North Carolina finished ahead of all Republicans even as Republican candidates collectively won more votes than Democrats, which helps to show the limitations of a traditional runoff system compared to ranked choice voting.)
Comparing votes cast for withdrawn candidates as active and inactive candidates: Among the withdrawn candidates, only Rubio and Carson won more votes as active candidates than inactive ones. For example, Bush as an inactive candidate has won at least 159,314 votes, while the active Bush won a total of 94,604. Rand Paul and Rick Santorum have won more than six times more votes as inactive candidates than as active ones, Mike Huckabee 13 times more votes, and Jim Gilmore 17 times more votes.
Image Source: Gage Skidmore