The stars of the European Union sit on banners flying outside the European Central Bank headquarters in Frankfurt, Germany, on July 20, 2017. Krisztian Bocsi | Bloomberg | Getty Images

The European Union is getting ready to vote on another key seat in European policymaking. The next vice president of the European Central Bank (ECB) will be elected shortly to replace Vitor Constancio, whose mandate expires in May. That vote will follow the December election of Portuguese Finance Minister Mario Centeno as Eurogroup president — a role that brings together the 19 finance ministers of the euro zone — and the January appointment of the Netherlands' Hans Vijlbrief as president of Eurogroup Working Group, which prepares the background work for Eurogroup meetings. So far, two names have been mentioned as potential replacements for Constancio: Spanish Economy Minister Luis de Guindos and Philip Lane, the governor of Ireland's central bank. All applications need to be summited to Brussels by Wednesday and the Eurogroup will publish a list of its suggested candidates on February 20th. Spain officially nominated Luis de Guindos as its candidate on Wednesday morning. European leaders will then hold a vote to select the ECB vice president at a summit in March.

Who could replace Constancio?

"The vice president is usually from a smaller country, because the larger countries get to be president," Erik Jones, Professor of European Studies at John Hopkins University told CNBC via email. "The current governor of the Bank of Ireland, Philip Lane has the inside track. He is very well-respected as an economist in addition to being a central banker. Moreover, Ireland has not had that position (before)." Lane has been governor of the Irish central bank since November 2015, when Ireland was trying to recover from its sovereign debt crisis. However, there's long been speculation that Spain's De Guindos could take the position in Frankfurt, Germany. He has previously run for other European seats, but withdrew from running a second time for the Eurogroup presidency at the end of last year. This was seen as a signal that he is seeking the ECB vice president role.

Constancio has been on the board for 7.5 years and has proved to be one of the intellectual forces within the ECB. Elwin de Groot head of macro strategy at Rabobank

"Spain has not been represented on the six-member Executive Board of the ECB since Jose Manuel Gonzalez-Paramo ended his eight-year term of office in May 2012," Michael Schubert, senior economist at Commerzbank, said in a note. "Spain's government representatives have therefore repeatedly called for a Spaniard to take over from the current ECB vice president Constancio." However, some members of the European Parliament, which also has a say on ECB appointments, are reticent in appointing a former minister given that the ECB needs to keep its independence from politics. "Constancio has been on the board for 7.5 years and has proved to be one of the intellectual forces within the ECB. Strong communication skills (as he/she needs to attend the regular press conferences) are key," Elwin de Groot, head of macro strategy at Rabobank told CNBC via email. He added that despite lacking a central banking background, de Guindos is the most likely choice.

Why does this vote matter?

European Central Bank President Mario Draghi at a press conference in Frankfurt, Germany, on January 19, 2017. Krisztian Bocsi | Bloomberg | Getty Images